In many medical practices it is necessary or desirable to heat a fluid before it is administered to a patient. For example, fluids such as whole blood and packed cells are stored in refrigerators at temperatures of approximately 4.degree. C. These fluids are often required to be administered to a patient within a short period of time after removal from the refrigerator. Rapid transfusion of cold blood often leads to systemic hypothermia. Because of the nature of the illness, trauma or medical intervention, many patients needing blood may already be hypothermic. The infusion of cold blood only adds additional insult to an already weakened system.
There is room for a limited number of trained medical personnel in the shock room. These individuals are involved in the flurry of activity that accompanies the arrival of a seriously injured or hypovolemic patient in the emergency center. (Maintaining an airway, assessing the patient, obtaining a history, establishing venous access etc.) As a result, crucial warming of blood and other hypothermic fluids is often delayed, or neglected entirely. In addition, the quickest electrical blood warmers take 5-10 minutes to reach operating temperature, which compounds the delay.
Great care must be exercised when heating certain physiological fluids in order to avoid damaging the cells by exposing them to too high a temperature. For example, whole blood or packed cells are damaged by high temperatures, and certain medicaments which might be in physiological solutions are sensitive to exposure to high temperatures. Thus, these conditions severely restrict the techniques used to quickly warm refrigerated or cooled physiological fluids.
Currently, apparatuses for warming physiological fluids, including blood, utilize either rapidly flowing hot water or electric heating elements as the source of thermal energy. These systems require large and/or complex equipment and skilled technical personnel for their operation. Additionally, the equipment usually requires a large amount of space, a commodity often limited in emergency situations.
The need for electricity makes currently available blood warmers inapplicable for use in the field and during pre-hospital transport, when the crucial initial steps of recussitation are carried out. This failure to warm the crystalloid volume expanders used during this phase of care initiates the steady drop in core body temperature seen in patients suffering from hypovolemic shock. Furthermore, conventional fluid warming must be discontinued for transport of the patient from the emergency center to the operating room.
There are reports of using exothermic or endothermic reactions to change the temperature of physiological solutions prior to injection. However, these reports provide no method to regulate the temperature. Furthermore, the systems described were designed to warm or cool small fixed amounts of injectable solutions, and could not be used to warm a continuous infusion.
Thus, it would be desirable to provide a device for warming physiological fluids which is compact, rapid, easy to use, does not require electrical input during its use and is self-contained and disposable.